The present invention relates to a method and apparatus for monitoring the integrity of an area and perimeter and for detecting intrusion within the monitored area or perimeter.
Area and perimeter monitoring and intrusion detecting devices are known which rely on the interruption of a light beam, either direct or reflected light beam, for detecting unauthorized intrusion through a door or window of a protected enclosure. Such devices generally consist of a plurality of light beams coupled with appropriate light detectors, strategically disposed over the protected area, or they take the form of radiation curtains with a plurality of radiation emitters aimed at sensors such that when one of the light or radiation beams is interrupted, an alarm is given.
One disadvantage associated with such systems is that they require a plurality of light or radiation emitters associated with a plurality of light or radiation detectors, and any malfunction of one of the elements causes a false alarm, or completely deactivates the system. In addition, they are easily defeated by skilled intruders as the diverse light beam or radiation emitters, and associated sensors, are stationary and the relatively narrow beams of light or other radiation have defined trajectories which may easily be avoided by crawling underneath the beams or jumping over the beams.